This invention relates generally to brazing apparatus and more particularly to such apparatus especially adapted to the fabrication and connection of microcomponents and microcircuits.
The use of electrodes to effect brazed or welded connections of small electrical components and repair of conductors by localized heating is well-known. The electrodes are positioned on the joint and electrically pulsed, often through a silver solder-coated braze repair ribbon, to generate a zone of molten metal to produce the attachment. Generally, a pair of electrodes are joined on opposite sides of an insulator and then machined to a small dimension at the working tip to enable access at the precise point in which metal fusion is to occur such as shown in U.S. Pat. Nos. 3,435,184 and 3,342,972. Although the tips can be made of various wear resistant materials, erosion eventually results from the repeated use of the electrodes, and they must be either replaced or re-machined to establish good contact and operable dimensions.
The replacement of electrodes results in a high cost. Not only do the tips have to be removed and finely and carefully machined to re-establish the original dimensions, but the reinstallation of the electrodes with precision is also time consuming, demanding slow and tedious adjustment. Even after installation of replacement electrodes, dressing and polishing is frequently required to maintain the tip surface optimally aligned to the characteristics of a particular brazing machine in which they are installed.
Brazing electrodes for this application typically have to withstand temperatures in excess of 1000.degree. F., while having a cross-sectional dimension at the tip of approximately 0.2 mm by 0.3 mm. They further have to be capable of carrying currents of 15 to 25 amps. Because of the energy handling requirements and the repeated use, the materials used as electrodes are necessarily harder, being comprised of tungsten or carbides or mixtures thereof. Because of this composition, machining of small tips on large-bodied electrodes is a difficult and time-consuming process.